-- 提出された回答を参考にした
import Data.List

hantei ds dmax pmax =
    if pmax == 0 then 0
    else if pmax `elem` ds then 1
    else maximum [c, 2]
    where
        c = ceiling $ fromIntegral (pmax::Int) / fromIntegral (dmax::Int)

main = do
    nstr <- getLine
    dstr <- getLine
    pstr <- getLine
    let
        n = read nstr :: Int
        ds = sort $ map read $ words dstr :: [Int]
        dmax = last ds
        pmax = maximum $ map (abs . read) $ words pstr :: Int
    print $ hantei ds dmax pmax